Thermionically assisted r.f. plasma assisted physical vapour deposition of stabilized zirconia thermal barrier coatings

In this work, yttria partially stabilezed zirconia has been deposited under a range of process conditions, by both electron beam physical vapour deposition (EBPVD) and radio-frequency plasma assisted (PA) PVD. The addition of thermionic assistance to the above techniques was also investigated. The effects of plasma assistance, thermionic assistance, pressure, surface finish and source-to-substrate distance on structure, phase, uniformity and adhesion are reported. PAPVD alone was found to improve adhesion and permit control of coating structure and densification over more conventional EBPVD coatings. The addition of thermionic emission for both PAPVD and EBPVD results in further improvements in adhesion and coating densification.